International Kiss Day: Science Explains Desire, Attraction, and Bonding

As the world marks International Kiss Day on April 13th, we delve into the profound scientific and evolutionary significance of this intimate act. Far from being a mere romantic gesture, kissing, documented as far back as 2500 BC in ancient Mesopotamia and Egypt, has served as a vital tool for social bonding and survival across diverse cultures for millennia.

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Cuando tenemos una relación segura, amorosa y cuidadosa, la corteza frontal domina a la amígdala (que gestiona el miedo). Esto permite que entremos en un estado de mayor calma

From a physiological standpoint, a kiss unleashes a cascade of neurochemicals. Experts like Nora Alma Fierro González from UNAM's Institute of Biomedical Research explain that this stimulus activates the nervous and endocrine systems, releasing neurotransmitters such as dopamine, oxytocin, serotonin, and endorphins. These compounds are intrinsically linked to feelings of pleasure and overall well-being. Furthermore, kissing positively impacts the cardiovascular system by increasing heart rate and dilating blood vessels, thereby improving blood oxygenation and helping to regulate blood pressure.

The immune system also benefits, as Fierro González notes the activation of the neuroendocrine-immune axis through emotional stimuli, which aids in the release of cytokines that regulate inflammation. Intriguingly, a 2014 study published in Science suggests that a mere 10-second kiss can exchange up to 80 million bacteria. This microbial exchange, according to the "hygiene theory," can actually strengthen our defenses by training the immune system. However, experts caution that kissing also presents risks for transmitting infections like mononucleosis, colds, or mumps.

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el beso romántico-sexual no surgió de forma abrupta en una sola sociedad, sino que se ha manifestado en diversas culturas a lo largo de milenios como una herramienta de vinculación y supervivencia social

Beyond the biological, kissing plays a crucial psychological and evolutionary role. Gabriel Gutiérrez Ospina, another specialist at IIBO, explains that kissing engages brain circuits involving the limbic system, amygdala, and prefrontal cortex. "When we have a secure, loving, and caring relationship, the frontal cortex dominates the amygdala (which manages fear). This allows us to enter a state of greater calm," he elaborates. From an evolutionary perspective, the U.S. National Library of Medicine suggests that romantic kissing serves as a mechanism for evaluating potential partners, analyzing "taste signals" to assess compatibility.

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en un beso de tan solo 10 segundos se intercambian hasta 80 millones de bacterias. Este intercambio de microbiota fortalece las defensas bajo la "teoría de la higiene"